U.S. Pat. No. 4,204,411, issued Dec. 8, 1981, Donald F. Wilcock and Martin W. Eusepi, co-inventors, entitled "Magnetic/Centrifugal Fluid Seal," assigned to Mechanical Technology, Inc., of Latham, N.Y., describes and claims a number of different novel, combined magnetic/centrifugal seal structures wherein both magnetic sealing is provided at standstill and at low rotating speeds and centrifugal sealing is achieved at high rotating speeds for a shaft journalled within a support housing.
A Vee-shape in the centrifugal section of the seal, with the Vee coming almost to a point at the outer extremity, has the advantage of minimizing the volume of fluid required to set up the centrifugal seal action. With the shaft at low-speed or stationary, the amount of fluid that is contained between the teeth in the central part of the seal during magnetic sealing is limited. When thrown out by centrifugal force this fluid forms the sealing fluid in the centrifugal section. The simple Vee-shape results in no wasted volume at the outer periphery, and therefore, more fluid volume available to set up a radius difference between the two sides to accommodate an imposed pressure difference during centrifugal sealing. A second desirable feature of the Vee-shape seal is available with very shallow or flat Vees where the side of the Vee lie within an angle of 5.degree. to 8.degree. of the shaft axis and provides a means for allowing large axial movement, or growth, of the shaft without having too much change in the tooth gap in the magnetic part of the seal. One still wants, however, to have a conical, or Vee-shape cross section so that when the shaft speeds up, magnetic fluid will flow toward the centrifugal section of the seal.